考虑气水两相流固耦合下可燃冰降压分解对井壁稳定性影响  

Effect of depressurization decomposition of combustible ice on wellbore stability considering gas-water two-phase hydro-mechanical coupling

作　　者：张玉[1] 李建威 畅元江[2] 李昊[3] 李大勇 ZHANG Yu;LI Jianwei;CHANG Yuanjiang;LI Hao;LI Dayong(College of Pipeline and Civil Engineering in China University of Petroleum(East China),Qingdao 266580,China;College of Mechanical and Electrical Engineering in China University of Petroleum(East China),Qingdao 266580,China;School of Petroleum Engineering in China University of Petroleum(East China),Qingdao 266580,China)

机构地区：[1]中国石油大学(华东)储运与建筑工程学院,山东青岛266580 [2]中国石油大学(华东)机电工程学院,山东青岛266580 [3]中国石油大学(华东)石油工程学院,山东青岛266580

出　　处：《中国石油大学学报（自然科学版）》2023年第1期148-155,共8页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(51890914,52179119);山东省自然科学基金项目(ZR2019MEEO01)。

摘　　要：海域可燃冰常赋存于低温高压深水浅层松散沉积物中,起胶结和骨架支撑作用;可燃冰分解相变,引起储层渗透率改变,直接影响气水两相流体的渗流特征与热质传递,制约可燃冰的持续分解;同时可燃冰的分解会降低含可燃冰沉积物储层的抗剪强度和承载力,降低井壁稳定性。考虑可燃冰分解相变、传热传质和气水两相渗流过程,基于流固耦合渗流理论,建立描述含相态变化的可燃冰降压开采热-流-固(T-H-M)耦合模型,对可燃冰储层降压开采气水两相流动规律、孔隙度和渗透率等物性参数演化规律进行描述,并对井壁稳定性进行研究。结果表明:随着可燃冰的分解,甲烷气体饱和度较水饱和度明显增大,井周气体饱和度明显高于水饱和度;储层发生塑性屈服后,塑性区内渗透率和有效孔隙度显著增大,而弹性模量和黏聚力大幅度减小;开采时间越长,生产压差越大,储层塑性屈服区域越大,井壁稳定性越差。Marine combustible ice usually occurs in deep-water and shallow loose sediments under the condition of low temperature and high pressure, which mainly plays an effective cementation or skeleton support role in hydrate bearing sediments. The permeability of reservoir changes with the phase change during the combustible ice decomposition process, which influences the flow characteristics and the heat and mass transfer of gas-water two-phase fluid. This behavior restricts the continuous decomposition of combustible ice. The decomposition of combustible ice will further reduce the shear strength and bearing capacity of combustible ice bearing sediment reservoir, which reduces the wellbore stability. A coupled thermo-hydro-mechanical(T-H-M) model was built to describe the phase change of combustible ice depressurization production process. The evolution rules of gas-water two-phase flow, porosity, permeability and other physical parameters during the combustible ice depressurization production process were described, and the wellbore stability was studied. The results show that the methane gas saturation increases significantly compared with the water saturation, and the gas saturation around the well is significantly higher than the water saturation with the decomposition of marine combustible ice. After the plastic yield of the reservoir, the permeability and effective porosity in the plastic zone increase significantly, while the elastic modulus and cohesive force decrease greatly. The longer the production time, the greater the production pressure difference, the larger the plastic yield area of the reservoir, and the worse the wellbore stability.

关 键 词：可燃冰 降压开采 气水两相流 物性参数 井壁稳定性 

分 类 号：TE375[石油与天然气工程—油气田开发工程]